The Dark Promise
by lickitysplit
Summary: Ban and Elaine are two immortals in love in defiance of their duties to the gods. When Elaine dies at the hand of a demon, Ban ventures into the Underworld in search of its mysterious king in order to win her back. Greek mythology AU, set after "The Dark Heart". Oneshot


**Summary:** Ban and Elaine are two immortals in love in defiance of their duties to the gods. When Elaine dies at the hand of a demon, Ban ventures into the Underworld in search of its mysterious king in order to win her back.

**A/N:** This is a oneshot for Elaine and Ban's birthdays to celebrate this ship I love so much! It is set after my fic _**The Dark Heart**_, which is a Greek mythology AU in which Meliodas and Elizabeth are Hades and Persephone. It is not necessary to read the other to understand this, but if you enjoy this please check out _The Dark Heart_ and its sequels, _The Dark Gift_ and _The Dark Fate._

Very many thanks to Galfridus who read through this for me.

* * *

"Is this what you like?"

The question is one he teases her with, one that makes her giggle with delight. "No," she whispers as he kisses her elbow. "Not there."

"Then where?"

The princess blushes and looks at him through thick lashes. "You know where."

The young man grins, propping himself up on his forearms. "You're going to have to be more specific."

He squeezes her thigh and she shrieks, "Ban! Stop that!"

They laugh as they kiss, the sun only peeking through the canopy of the forest. This is their safe place, the spot they can meet away from watchful eyes. In the warm glow of late autumn, her hands smooth over his arms and his lips tug on her skin, both filled with the joy of youth and love, where death does not touch them. Ban is the cupbearer of the gods, and so has been given eternal life. It is an honor he had exalted to receive, his long years as a boy cast out by his parents and taken in by a thief now over. He lives in the luxury of the Celestial Realm, his sworn duty to serve them earning him comforts he had never dreamed, and a life neverending.

Most pleasing of all has been meeting the Holy Maiden, the protector of the forest. The moment his eyes had laid upon her Ban was lost; luckily for him, Elaine had felt the same way. Many days passed of longing looks and biting lips, until finally he caught her alone, and with breathless laughter they began to learn of one another. Both innocent, their love is pure, but steadily moving towards the inevitable, which is forbidden to him, a servant of the gods.

"Where then?" he grins, his teeth flashing and reminding Elaine of a wolf from the stories.

"Perhaps… here?" Elaine points to her neck, and Ban obliges. He leaves a long, open-mouthed kiss on her pulse point that has her panting in moments.

"Where else?" he growls.

"Lower," she breathes.

Ban kisses her slowly over her collarbone and down the front of her dress. The fabric forms a low v-neck that reaches nearly to her navel, and there is not an inch of exposed flesh left untasted. So when she reaches up and pulls the fabric open even more with trembling fingers, Ban gives a groan and presses his face to her exposed breast. "You are so beautiful," he murmurs.

"Am I?" she teases, carding a hand in his wild hair.

"Mm hmm. And you are mine."

"Greedy," she laughs, and then he runs his tongue over her nipple, lapping until it is a stiff little peak. His hand pulls back the fabric covering the other, grabbing her almost roughly, but Elaine only squirms beneath his large body and arches up into his touch.

Ban gently nibbles the underside of her breast. "Here?"

"Yes, oh yes." She sighs and closes her eyes. "I want it all."

"Now who is the greedy one?" he says, his hands sliding beneath her dress.

She stills as his palms cover her bare thighs. "I am," Elaine admits. "I want…"

His lazy kisses on her stomach stop, and then Ban is leaning over her again. "What do you want?" he says. "I'll give you anything."

"I want to be yours." She wraps her arms around his neck. "I want to belong to you, not the gods."

The words slip out, as foolish as they are. Elaine nearly jolts in panic at her blasphemy: it is one thing to keep desires in one's heart, but to say such things aloud! She blushes a deep rose and turns her face away in shame; but Ban only grins, lowering himself to cover her body and grind between her legs. "Let's do that then," he says, bringing his face close enough to brush his nose along her cheek. "I'll steal you away. I was a thief, you know."

"Ban…" Her arms tighten around him.

Her dress rides up as he presses between her thighs. "Someday I will steal you, my princess," he says, and the words weave between them. "Someday I will make you mine."

"Yes please, please," she whispers against his ear.

She cries out as he enters her body, and their fates are sealed with a promise. Neither know the power of these words that are lost in the pleasure of an autumn afternoon, but their oath is sealed nonetheless.

* * *

The gods mourn the loss of their Holy Maiden, who falls to a monster from the Underworld. These things happen, they say, but Ban shakes as he holds the chalice, tears flowing freely from his eyes and splashing to the floor. Even the immortals can be killed, for life may be eternal but never comes with guarantees. And as the days stretch on and another is anointed as saint, the loss of Elaine becomes heavier with each morning.

Now Ban knows the curse that is immortality.

_The Underworld, the Underworld,_ the cursed realm of the dead, the words rolling in his mind and haunting his dreams. Where is this place, that can produce such demons? This one was bent solely on destruction, made for torture, its existence carnage. The ones responsible for the breach made reparations, and it was over, or so the gods had said.

But Ban feels the loss too deeply. What if it was his fault? Instead of some random bit of misfortune, his actions had caused the universe itself to deal justice? Ban is forbidden from anything but his service; yet he had taken the Holy Maiden as his own. They had shared whispers of freedom, and escape, and forsaking the gods themselves for each other. What if that heresy had brought forth a demon?

Surely they would know, and that alone is enough for him to know it is not _his_ fault, or Elaine's. It is a calamity of chance, nothing more, and now, Elaine is in the Underworld.

He wonders what it looks like, do demons live there? Is the king as foul a creature as the one who had escaped into Britannia? There are rumors about him, that he is black as a crow and eats the souls of virgins, that sins are punished, that the pure are rewarded. A story was told once that many years ago he tried to eat the soul of a goddess, and her death brought winter to the world; but others say she went there of her own accord and seduced the dark king with her beauty. Ban suspects the first version is true, for how can such a creature love?

There is another story too, that the goddess had given her life to save the demon. She taught him how to love, as impossible as that sounds. But perhaps the king can love after all… and if he can, then he can feel pity as well…

He wonders too of the souls that wander there. Is Elaine there? Is she in Paradise, or Hell? She was an innocent, her life blameless—except for their one moment of indiscretion.

The thought fills him with fear. What if she is being tortured right now, because of him? What if Elaine is suffering because of their love, because of the oaths to the gods now broken?

_Who cares?_ his mind argues. The gods did not keep her safe, the gods did not stop her death. Ban has served his duties faithfully and in return his love is dead. An apology was made and accepted, and all moved on except for him. How could they do this? How can they live on when she does not? How can Ban?

Shame now presses against his chest, and Ban decides he must find a way.

* * *

Meliodas traces his fingers along Elizabeth's arm, smiling to himself. She had been returned to him for several weeks now, but still he marvels at having her in his embrace again. The goddess shivers and gives him a kiss on the cheek. "Are you well?" she asks.

She shifts in his lap, which is where the queen often spends her time when he is wrapping up his work. His hand snakes around her hip, his imagination igniting as he imagines the soft flesh beneath the silk, and the king's gaze goes hooded as he thinks of what will come later, after dinner. _Or perhaps as an appetizer?_ he muses to himself.

Just as he decides to lean in for a kiss the entrance of someone or something foreign catches his attention. Elizabeth notices just a second later, and the queen jumps to her feet and moves down the dais. "Stay back," he commands, readying his power. A threat? Someone come to claim Elizabeth, take his powers, take his throne? Let them come, for he can tear them apart in his own realm.

Instead the doors open and in the doorway stands a tall, lanky man, hands on his hips and head cocked to the side. "Is this the Underworld?" he calls.

"Who are you?" the king shouts. "This is my domain. You have no leave to be here."

He assesses the intruder and finds him immortal, which explains how he got this far; his power is strange, however, and not unlike Elizabeth's. Meliodas looks to the goddess, who meets his gaze and shakes her head, indicating she does not know him either.

"Are you in charge here?"

Meliodas draws back in shock. The impertinence! And now the young man is striding forward again, so he calls upon the magic of the place to protect its queen. Thick tendrils of black rise from the floor and capture the man in a vise grip, weaving around him until his limbs are pulled out and only his face can be seen.

"Who are you?" The king demands, and his tone makes it clear he will not ask again.

"My name is Ban," he chokes in answer. "I am looking for the Lords of the Underworld. Are you a king?"

Meliodas bristles a bit, and the tendrils tighten in response to his mood. Slowly the demon approaches, regarding the stranger and examining him closely until he can take a whiff off him. "You smell like a human," he observes, "although you have power _and_ the grace of immortality. How can this be?"

"Former human," Ban offers. Meliodas straightens and looks up into his eyes. He is easily a foot taller, but bound as he is the man looks almost comical. He gives a slight nod and the vines relax enough to allow him to breathe and answer.

"Former?" prompts Meliodas.

"Yes," comes the answer through gritted teeth. "I was allowed to drink from the cup I now bear for the gods."

Meliodas huffs. "I see. And what are you doing here? This is the realm of the dead, and you are _un-_dead."

"Ban the Undead. I rather like that, it has a bit of a ring—" The vines tighten again and he chokes, "Fine! I have a request to make, if you'd allow me to speak. I'll answer any question you want."

"A request," the king scoffs folding his arms. "Foolishness. There is nothing one such as _you_ could want from _me_, and there is nothing _you_ could possibly have to offer that I would ever want. How did you get here?"

"The Necropolis."

"I'll have it shuttered immediately. How did you get past the guardians?"

Ban frowns, irritating him further. "What guardians?"

"What guardians!?" Meliodas cries. " The beasts that keep humans and the like away from my kingdom. There is a hound of impossible size with razor sharp teeth and a mouth large enough to swallow you whole, and a boar whose—"

"Oh!" he interrupts. "You mean the dog and the pig?" Meliodas grits his teeth as Ban laughs. "I thought they were your pets greeting me at the gate. Nothing a bit of my cooking didn't sort out. We are great friends now, they even pointed the way—"

"Friends!" shouts Meliodas. "You cannot be _friends_ with my guardians! You mean to tell me you overcame them with _food?"_

"A bit of cooking, yes," Ban grins. "I had some leftovers in my pocket, you see."

"Enough!" Meliodas is truly furious now, but what stops him from tearing the limbs from the man is the tinkling of laughter behind him.

He turns to spy Elizabeth hiding a smile behind her hand. "That must have been some remarkable cooking," she giggles.

The demon frowns indignantly, swerving back when the immortal says, "I'd be happy to serve you some time, my lady. After all, my life is service to the gods."

They share another laugh, but Meliodas is not amused. "Well _this_ god is ready to test the limits of your immortality," he growls. "Now state your business so I can be rid of you."

"It's simple, Your Grace," he answers, his eyes narrowing as his smile turns up devilishly. "I've come to kill you."

* * *

The hall is now silent with the confession. Ban eyes the king, tensing in case he strikes. Despite his demeanor Ban knows the very real, very ancient power that dwells within this god. They are nothing alike, and he knows he is well out matched.

Yet he meets the king's dark glare, ant joviality now gone. "Kill me," the demon deadpans. "You cannot kill a god."

"I would have said the same, only one was killed not long ago." Ban swallows thickly against the sting of memory. "Her name is Elaine. She was daughter of the forest. She was the Holy Maiden, the saint of the Great Tree and she was killed. By one of _your_ demons."

He watches with a twisting satisfaction as Meliodas works his jaw. "I know of that business," the king finally replies. "An earthquake had torn a hole in the seal between worlds. One of the creatures of Purgatory escaped. It was not intentional, and my brother retrieved it almost immediately, before it could do too much harm."

"It did enough!" Ban shouts. "It killed her, and now she's here, here with you, instead of…"

He is struggling in the bonds, his fury and grief fueling him to try to break free. But it is useless, and Ban feels his limbs go weak as sorrow bows his head. His vision swims and his breathing shudders. How can he do this, when just the thought of Elaine takes his strength away?

A hand touches his face, warm and inviting. When Ban looks up he sees the queen standing before him, her palm glowing as she strokes his cheek soothingly. "You loved her, didn't you?" she sighs. "And she loved you?"

"Yes," he whispers.

"I'm so sorry for this loss and this pain."

Incredibly, the queen sheds a tear, and he watches as it slides down her cheek, hanging like crystal from her face. "I want her back," he says pleadingly. "I promised her I would make her mine."

The queen smiles sadly. "Promises are dangerous things." She glances over at the demon, who is watching with a scowl. "Will you release his bonds?"

"No." The king glares at him. "First explain this futile plot for revenge."

"It's not revenge," Ban snaps. "I consulted the goddesses of life. Their queen spoke to me through an Oracle."

He notices the surprise that registers in both monarchs' faces and rushes on, "She said if I killed you then I could release any soul I wished from the Underworld. She offered me aid in my quest." Ban lifts his chin defiantly. "A goddess of life would not lie."

The queen seems distressed, turning away. Meanwhile the king says, "Maybe, maybe not. But how are you to know it was a goddess and not some trick?" Ban frowns, trying to stutter out an answer, when Meliodas scoffs, "You can't know. And what you were told is utter nonsense. There is no way for you to kill me, and even if you managed it, it would not grant you authority over this realm."

"But—"

"It's true," Elizabeth interrupts, her voice drawing both of their attentions. "I am a goddess of life. None of us can speak through an Oracle. It was a trick, to send you on this errand in the hope to use you to hurt my husband."

The blood seems to leave his body, and Ban struggles to take in a breath. "I don't accept that!" he shouts. "There has to be—has to be something!" His eyes dart to the king. "I'll fight you anyway. I'll take your throne and then I can make her my queen."

He expects the demon to react in anger, perhaps lash out at his audacity. But Meliodas is calm as he replies, "Death comes for us all. There is no stopping it, when it decides to claim a life. But I… I understand." The king reaches out a hand. Ban watches as the goddess moves to entwine her fingers with his, the sight making his eyes water. "Your resolve and your love are so plain, I would give you the chance to kill me, if I could. But it is impossible: I am king and that cannot be changed, even if you had the strength to win."

Ban nods, and he finds the tendrils loosening a moment later, until he is standing on the ground with his head bowed. "I don't know what to do," he says.

The room is quiet, heavy with sorrow. Ban looks up and spies a door to the side, and his soul stirs. "Is that where she is?" he asks.

"She is in Paradise," Elizabeth says. "Your Elaine was found blameless. She has a beautiful heart," she smiles.

Ban sighs. "I suppose I could not see her again?"

"Only those who face trial and are judged can step through that door," she explains. "Unless you have leave from the king."

His brows draw up in surprise. "Then give me leave! Let me go there! I can—"

Meliodas cuts him off with a shake of his head. "If I allowed every mourner to enter Paradise, this would be the land of the living instead of the dead."

"Then give me the trial," growls Ban. "Let me do _something_. I came all this way, I'm this far, and she's right _there!_ I can give you something, or give me a test—a challenge. I will challenge you!" He points at the king. "I challenge you to a contest! If you win, I will leave and never return, but if I win, you will let me see her again!"

The demon's lips twist as he tries not to smile despite his annoyance. "There is nothing you could do to beat _me_ in a contest."

"Unless it was a cooking contest," Elizabeth laughs.

The king looks at her sharply, which makes her laugh even harder; finally even the demon relents, shaking his head with a chuckle. "Perhaps that."

"An arm wrestle," Ban suggests. His mouth tilts upwards when he sees a flicker of interest on the king's face. "Best two out of three. I could win easily when I was human. Will you put your honor on the line?"

* * *

"There!" Meliodas cries in triumph. "That is 361 wins for me!"

Ban glares at him over the table, flexing his fingers. "No, that is only 360. _I_ have 361."

"What?" the king scoffs. "Impossible! I don't lose."

"You have 361 times!" argues Ban.

Meliodas opens his mouth to respond when Elizabeth interjects, "Don't you think it's been decided?"

Both men turn to stare at her in confusion. She looks between them and chuckles, "You've been doing this for quite a while. I think Ban has earned his reward."

Elizabeth tilts her head to him, and Ban gives the king a grin. "See? Even the queen says so."

With a string of muttered curses that set them off laughing again, Meliodas grumbles, "Fine then. I'll allow her to come into the hall."

Ban nearly stumbles as he rushes to stand. "You will? You'll let me see her?"

"Against my better judgment… yes." He nods to Elizabeth, who disappears behind the door, Ban watching in awe as she leaves. "But you cannot leave. You'll have a few minutes to speak, and then you _both_ return to where you belong."

He stammers out his agreement and thanks. Meliodas moves to the side as moments later, the door opens again.

Elaine stands before him, and Ban would never remember his moment precisely: what she was wearing, what she said, her hair or her smile or how many steps it took until she was in his arms. What he knows is she is _here_, somehow solid and warm and their mouths seal together in a kiss that is bittersweet.

He whispers her name when they break apart, and she says, "Oh Ban… I wanted to see you for so long…"

Ban cuts her off with another kiss, lifting her easily against his tall frame as her arms curl around his neck. Supporting her waist with one arm, the other he uses to slide his hand into her hair. He drinks her in; he cannot get enough of her. Nothing he had tasted, not even the water from the eternal cup that the gods granted him to become immortal, compares to the fresh, cool sapor of her lips.

Her touch is feather-light, even moreso than when she was alive. He presses his cheek to hers, breathing deeply. "You came for me," whispers Elaine. "But I can't—I can't go with you—"

"I know," Ban replies, his voice harsh. "But I promised! I promised I would make you mine, that I would steal you away."

He looks into her eyes, which are dulled of the sparkle that had always been in the corner of the amber irises. For a moment, he pictures it: taking off in a run, Elaine in his arms, his feet and heart thudding as he tries to escape the Underworld. Could he do it? The guardians would not be an issue, but Meliodas is king here. A snap of his fingers would have him caught, and Ban has already done enough to defy the gods, by sharing pleasure forbidden to a cupbearer and entering this forbidden place.

Her fingers are soothing on his temple, and she kisses his forehead. "I wish we could have had… just one last time together," he murmurs.

Elaine's lips flutter on his cheek. "All I wanted was for you to hold me like this, one last time."

Ban pulls her tighter, his fingers clenching against her back. "This—this can't be the last time! I made a promise, a _promise,_ and…"

Suddenly he pulls away, and looks over at the king and queen. Meliodas' face is grave, his lips tight as he observes them in silence. On his arm, Elizabeth cries quietly, wiping her tears away, her head tilted to press comfortingly against the demon's. "You're here," he says to the goddess, who blinks in surprise at him. "The stories say so many things, but they all end with you—the two of you—being apart. But you're here, together, a goddess of life and the king of the Underworld. So how? How did you do it?"

Meliodas clears his throat, but it is Elizabeth who speaks. "I gave the king half of my heart," she replies with a sad smile. "I used my power to give him a gift."

Ban's lungs tighten. "Then so can I." He cups Elaine's face, her eyes wide and searching his, and he says, "This isn't the last time. I'm going to give you a gift."

"Wait!" the king calls, but Ban ignores him and closes his eyes. Deep inside, he finds that silvery feeling that runs through his veins, the one that keeps him from getting sick, the one that closes wounds and wipes away bruises. He grabs hold of the feeling and _pulls_, forcing the warmth through his palms and into Elaine. Ban hears her gasp, jerking a bit in his hands, but he does not stop, not even at the shouts from the king, or when he feels hands pressing on his arms.

He is panting when he opens his eyes, and to his relief, Elaine's stare back. Yet now they are bright, dancing as she says, "Why did you do that?"

"I can't live without you," he says simply.

"Are you sure about this?" Her fingers curl around his biceps. "You've given up your immortality, to bring me back to life."

"I don't care about that," laughs Ban. "As long as I get to keep my promise to you."

He can feel the tension behind him, and he turns, ready for the demon's wrath. What he finds instead is the queen smiling brilliantly, her fingers entwined with the king's. "You're both human now," he says. "I don't know how you did it, but both of you have a new life."

"I made a promise," Ban replies, turning so he can hold Elaine's hand and face the king. "If there is a punishment for that, if I must pay with my own life, then I am ready."

Meliodas shakes his head. "No. You were immortals when you made your promise; an oath between gods cannot be broken." His mouth then quirks up. "Go. You are free to live in Britannia now, away from your service. But one day you'll return here, so be sure your hearts are pure when that day comes."

"Don't worry," he grins. "If you're to send me to torture, I'll just arm wrestle you for it."

The king's brows go up in shock; then he leans his head back and gives a great laugh that echoes in the hall. "Go then," he waves them away. "Your guardian friends can show you the way."

Ban swallows thickly before giving a deep bow. Next to him, Elaine curtseys, and then takes his hand again. "Until next time," he says, and they leave the Underworld together, to begin their new lives as mortals.


End file.
